Don’t be stumped 🙂 In cases of sudden QoS degradation, there is only 2 solutions :
1. (highly problable) SW bug
2. (unlikely) HW failure
So try to reset your BTS (each element, one by one, including the TCU board at BSC side)
And check the QoS.
If it is still bad, then it is probably linked to the HW…
It did happen once that a BTS had a high HO incoming failure (100% !!) and the only choice we had was to change the BTS (luckily it was a micro bts). It wasn’t software… After the change, everything was fine again.